1. Field of the Invention
The present invention relates generally to improved methods of stimulating wells in unconsolidated or poorly consolidated formations, and more particularly, to methods of stimulating hydrocarbon fluid production from such wells while preventing the migration of sand with the fluids produced therefrom.
2. Description of the Prior Art
Oil and gas wells are often completed in unconsolidated formations containing loose and incompetent or poorly consolidated sand which migrates with oil, gas and/or water produced by the wells. The presence of sand in the produced fluids is disadvantageous and undesirable in that the sand particles abrade pumping and other producing equipment and reduce the fluid production capabilities of the produced zones in the wells.
Incompetent subterranean formations include those which contain loose sand that is readily entrained by produced fluids and those wherein the sand particles making up the formations are bonded together with insufficient bond strength to withstand the forces produced by the product of fluids from the formations. A technique which is often used for minimizing sand production from such formations has been to produce fluids from the formations at low flow rates whereby the near well stability of sand bridges and the like in the formations are preserved. However, the collapse of such sand bridges often occurs as a result of unintentional high production rates and/or pressure cycling. Pressure cycling occurs from frequent shut-ins and start ups of a well. The frequency of pressure cycling is very critical to the longevity of the near well formation, especially during the depletion stage of the well when the pore pressure of the formation has already been significantly reduced.
Heretofore, weakly consolidated formations have been treated by creating fractures in the formations and depositing proppant in the fractures to maintain them in open positions. In addition, the proppant has heretofore been consolidated within the fractures into hard permeable masses by hardenable resin compositions to reduce the migration of sand through the fractures with produced fluids. Very often, to insure that sand is not produced, costly gravel packs, sand screens and the like have been installed in the wells. Since gravel packs and sand screens filter out sand from the fluids being produced, the presence of the filtered sand adds to the flow resistance thereby producing additional pressure draw down which causes the fracture faces and other portions of the unconsolidated formations to break down and the consolidated proppant in fractures, gravel packs and the like to be bypassed.
Thus, there is a need for improved methods of stimulating fluid production from unconsolidated permeable formations penetrated by wellbores while preventing the migration of formation sand with fluids produced therefrom.